1. Field of the Invention
The present invention relates to a mechanism for pivotally locating a vertical seat back with respect to an associated horizontal seat cushion in an adjustable manner. More specifically, the present invention relates to an automobile seat recliner which can be adjusted to locate a seat back in any given position.
2. Description of the Prior Art
Seat recliners are used with vehicle seats to control the angular orientation of a vehicle seat back with respect to an associated horizontal seat cushion. Adjustment of the angular orientation of the back with respect to the cushion affords a vehicle driver or passenger comfort in assuming a position that meets with the seat occupant's size and desired position while seated. Conventionally, recliners have been limited in the number of positions to which the seat back can be oriented with respect to the seat cushion. Also, when utilized with front seats in a vehicle of the "two-door" type, the seat back must be able to pivot forwardly independent of the seat cushion to an easy enter position to allow a person to enter or leave the rear seat behind the front seat.
There have hitherto been many examples of infinitely variable seat back adjusters. Many of these mechanisms have difficulty in producing a locking force which is great enough to withstand the impact loadings on the seat back required for occupant safety. In addition, many of these reclining mechanisms are very complicated and, consequently, expensive to mass produce.
An example of an infinitely variable seat back adjuster is that shown in U.S. Pat. No. 4,070,058, issued Jan. 24, 1978 to Anthony A. Muehling. This patent discloses a seat reclining mechanism mounted on the seat cushion and the seat back and contains a pair of cam members pivoting about a axis within a housing. These cam members engage a cam surface on one end and a locking surface on the other end so that rotation is resisted by the forcing of the cam member into locking engagement with the locking surface by attempted movement of the other cam surface. A mechanism of this type does not appear to produce the positive locking forces inherent in the present invention. Also, a large number of parts are required, thereby, making the seat reclining mechanism expensive to produce.
U.S. Pat. No. 3,423,785, issued Jan. 28, 1969 to J. Pickles discloses a position control mechanism which uses a cyclic gearing to produce substantial rotation of a friction drum upon limited rotation between the seat back and the seat cushion. The friction drum is bound with a spring coil which acts as a friction brake and, thereby, locks the seat back and seat cushion from relative rotation. Again, the locking forces developed by this scheme appear to be less than those developed by the seat reclining mechanism of the present invention. A similar seat reclining mechanism is shown in U.S. Pat. No. 3,508,294 which issued on Apr. 28, 1970 to the same inventor.
U.S. Pat. No. 3,315,298, issued Apr. 25, 1967 to W. Strien et al. discloses several embodiments each of which employ a helical camming surface on a rotatable plate to position an element fixedly attached to the seat back. Movement of the seat back is resisted by the element being moved generally perpendicular to the camming surface. Since only a small inclined angle exists between the element and the camming surface, the camming surface will not rotate because a friction force applied to the camming surface plate has a mechanical advantage due to the small angle. The forces produced by this scheme are still relatively less than the forces developed by the mechanism of the present invention. Furthermore, the helical surfaces are expensive to manufacture and not easily suitable for mass production.
U.S. Pat. No. 3,237,987, issued Mar. 1, 1966 to J. James discloses a locking mechanism which utilizes two sets of rollers each of which may be wedged between a cylindrical surface attached to seat back and a fixed inclined surface. Any movement of the seat back rearward or forward causes one or the other set of rollers to engage the inclined surface which further wedges the rollers against the cylindrical surface. The frictional forces thus developed keep the seat back from moving. Movement of a release mechanism in one direction will allow the seat to be moved in the opposite direction only since only one set of rollers can be displaced from the wedging surfaces at a time. It has been found that the mechanism of the present invention is far cheaper to mass produce than that disclosed in U.S. Pat. No. 3,237,987.
Other examples of infinitely variable seat reclining mechanisms are disclosed in U.S. Pat. Nos. 2,112,265 and 3,195,952.
The seat reclining mechanism of the present invention utilizes a self-energizing double wedge arrangement to effect locking. The inventor has used a similar idea in his limited slip differentials disclosed in U.S. Pat. Nos. 3,572,165 issued Mar. 23, 1971 and 3,762,241 issued Oct. 2, 1973. These patents deal with a clutch arrangement which would not suggest their use in a seat reclining mechanism.